1. Field of Use
The present invention relates to control units and more particularly to a microprogrammable control unit which provides for increased processing efficiency.
2. Prior Art
In general, a substantial number of central processing units (CPU's) employ microprogrammed control units for executing program instructions. In order to reduce the size of the control store and to increase processing efficiency, a number of control units have employed two control stores. Examples of such systems are disclosed in U.S. Pat. Nos. 3,949,372, 3,953,833 and 4,001,788. While such systems provide such advantages essentially all of the processing of an instruction proceeds under microprogram control. Moreover, normally separate sequences of microinstruction or additional microinstructions are required for processing different program instructions specifying load and store operations involving different program visible registers or program instructions involving updating register operations.
It is a primary object of the present invention to provide a microprogrammable control unit which has reduced storage requirements.
It is a further object of the present invention to provide a two control store microprogrammable control unit which provides for increased processing efficiency.